1. Field of the Invention
The invention relates to an electric rotary actuator that includes an electric motor and a speed reducer.
2. Discussion of Background
In related art, there is an actuator that employs an outer rotor electric motor as described in Japanese Patent Application Publication No. 2004-274838 (JP-A-2004-274838) and Japanese Patent Application Publication No. 2008-6888 (JP-A-2008-6888). In an outer rotor electric motor, a stator that serves as a heat source is located on the inner side of a rotor. Therefore, it is important to ensure a heat dissipation path from the stator.
The actuator described in JP-A-2004-274838 is formed so that fins extending in the axial direction are provided on an opposite side of an inner stator in the axial direction from a speed reducer to thereby exhibit a heat dissipation effect on the inner stator. In the actuator described in JP-A-2008-6888, an inner stator is fixed to a motor cover provided on an opposite side from a speed reducer to thereby dissipate heat from the stator that serves as a heat source to the outside via the motor cover.
However, in the actuator described in JP-A-2004-274838, the fins are formed to extend outward in the axial direction, so the length of the actuator in the axial direction increases. In addition, in the actuator described in JP-A-2008-6888, the motor cover needs to have a sufficient thickness in order to exhibit a heat dissipation effect. Therefore, when the thickness of the motor cover is reduced in order to reduce the axial size and the weight, heat dissipation performance decreases, so it is difficult to obtain a required heat dissipation effect.